The distribution of spectroscopic strength in nuclei can be extracted from direct reaction cross section measurements, as one-nucleon knockout at intermediate energy or transfer at low energy. The study of deeply-bound nucleon removal from several sd-shell nuclei having a large di erence of separation energies S = Sp��Sn \' 20 MeV, exhibits experimental cross sections about four times smaller than theoretical predictions from state-of-the-art calculations. This trend is not observed from (d,p) transfer reactions with nuclei having smaller separation energy asymmetry, up to S \' 12 MeV. To investigate the origin of this reduction, we have performed two complementary experiments for the 14O case having a large energy asymmetry : (i) one-nucleon knockout from 14O (53 MeV/n) and 16C (75 MeV/n) on a 9Be target at the NSCL ; (ii) one-nucleon transfer reaction using a SPIRAL beam, 14O(d,t)13O and 14O(d,3He)13N at 18 MeV/n, and the MUST2 array. The analysis of the data presented in this document leads to a discrepancy between the spectroscopic factors extracted from these two experiment when a deeply-bound neutron is removed from 14O. In the neutron knockout from 14O, the cross section is strongly reduced compared to predictions based on an eikonal model and shell model spectroscopic factors. Moreover, several deviations from the eikonal prediction are observed on the shape of the parallel momentum distribution of the ejectile 13O. For the transfer 14O(d,t)13O, such a reduction is not observed and results are in agreement with stable nuclei values. These results call for new theoretical developments concerning the description of the reaction mechanism when a deeply-bound nucleon is removed from a nucleus.